1. Field of the Invention
The present invention relates to a drive system which transmits a drive force to a photosensitive drum of a process cartridge detachably mountable to an image forming apparatus. The present invention also relates to an image forming apparatus which includes the process cartridge.
2. Description of the Related Art
In image forming apparatuses such as a printer, a facsimile machine, and a copying machine, a photosensitive drum is charged uniformly by a charging unit. An exposing unit selectively exposes the photosensitive drum according to image information scanned by an image reading unit or received facsimile data. Then, electrostatic latent image is formed on the photosensitive drum. A developing unit forms a toner image on the electrostatic latent image. A transfer unit transfers the toner image onto a paper fed from a paper feeding unit, and the image is recorded on the paper.
A conventional process cartridge integrally includes a photosensitive drum, a charging unit, a developing unit, and a cleaning unit. The process cartridge is detachably mountable to the image forming apparatus. The process cartridge includes the photosensitive drum, and at least one of the charging unit, the developing unit, or the cleaning unit.
An electro-photographic typed image forming apparatus, which uses an electro-photographic image forming process, includes a photosensitive drum, and a process unit which is actable to the photosensitive drum. In the electro-photographic typed image forming apparatus, a process cartridge is used as a unit which is detachably mountable to the image forming apparatus. By using the process cartridge, it is not necessary for a user to depend on a service worker, and the user can carry out the maintenance of the machine. As a result, operationality is improved. For example, even when the amount of toner remaining in the process cartridge becomes low, or when there is a failure in the photosensitive drum, if the process cartridge is replaced with a new cartridge, the image forming apparatus can be recovered to a normal state.
A drive system for the photosensitive drum in the process cartridge type is desirable to have a structure in which the process cartridge can be easily detachably mounted to the image forming apparatus, and a drive force is transmitted accurately to the photosensitive drum.